|Publication number||US7483560 B2|
|Application number||US 10/679,290|
|Publication date||Jan 27, 2009|
|Filing date||Oct 7, 2003|
|Priority date||Jan 17, 2003|
|Also published as||US20050100205|
|Publication number||10679290, 679290, US 7483560 B2, US 7483560B2, US-B2-7483560, US7483560 B2, US7483560B2|
|Inventors||Chle Shishido, Ryo Nakagaki, Maki Tanaka, Kenji Watanabe, Yuya Toyoshima|
|Original Assignee||Hitachi High-Technologies Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (1), Classifications (15), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to a method which is used for measuring a three dimensional shape of a fine pattern formed on a semiconductor device, such as a semiconductor memory or an integrated circuit.
SEMs (scanning electron microscope) are used for measuring fine patterns that are formed on semiconductor devices. The SEM obtains an electron beam image of a sample by detecting secondary electrons and reflected electrons that are generated when an electron beam is irradiated onto the sample. The most popular SEM used currently in semiconductor processing is called a critical dimension SEM, which measures a sample mainly by using a secondary electron beam image.
In semiconductor processing, the critical dimension SEM has been conventionally used for optimizing the conditions of a manufacturing machine, such as an aligner and etcher, or for monitoring process fluctuation. However, with refining of the patterns, three dimensional shapes of the samples need to be measured in various cases, wherein the critical dimension SEM is not always useful.
Examples of related technology for measuring cross sectional shapes are as follows.
(1) After a wafer is cut or FIB-processed, a cut surface of the wafer is observed using an electron microscope.
(2) The cross sectional shapes are observed using an AFM (Atom Force Microscope).
(3) The cross sectional shapes are observed using scatterometry. However, in these methods, the following problems are encountered.
In the method (1), it takes a long time to prepare for observation of the cross sections. Additionally, the cut or FIB-processed wafers tend to become contaminated, and, thus, they cannot be completed as products. As a result, this method cannot be used for process fluctuation monitoring in a quantity production process.
The method (2) does not take a longer time than that in the method (1) to observe the cross sections; however, the AFM has a low throughput, which is about ⅓ of that of the popular critical dimension SEM, and it cannot be used to measure all patterns because of restriction of the chip shapes. Consequently, as it is near-meaningless, critical points cannot be measured in the monitoring of process fluctuation in which measurement of three dimensional shapes is required.
Recently, the scatterometry method (3) has received attention, because it can be operated at high speed, and it can be used to measure cross sectional shapes non-destructively. Using the fact that spectral distribution of scattered light from a sample changes depending on the material and cross sectional shape of the sample, the scatterometry method matches the spectral distribution of the actually-measured sample to the spectral distribution library of various cross sectional shaped models previously produced using offline simulations, thereby to indirectly measure the cross-sectional shape of the sample (see
Technology related to the present invention is disclosed in JP-A No. 141544/1991, JP-A No. 342942/1992, and JP-A No. 506217/2002. However, the technology disclosed in these publications have the following problems. The critical dimension SEM, which is popular in semiconductor processing, can measure plane shapes by use of electron beam images of arbitrary patterns, but it cannot be used to measure three dimensional shapes. The scatterometry method can measure three dimensional shapes, but the sample patterns are limited to lines and spaces. Therefore, the scatterometry method can be used to measure only those shapes which conform to the test patterns produced for measurement.
The present invention provides a method which is capable of measuring a three dimensional shape of an arbitrary fine pattern formed on a semiconductor device, in other words, a method that is capable of measuring a three dimensional shape not limited to a test pattern.
In accordance with the present invention, an optical measurement system, such as a system which uses the scatterometry method, measures cross sectional shape information about a test pattern, an electron microscope obtains an electron beam image of a fine pattern, and plane surface information about the fine pattern is obtained from the electron beam image and is combined with the cross-sectional shape information about the test pattern so as to measure the three-dimensional shape of the fine pattern.
Additionally, in accordance with the present invention, an optical measurement system, such as a system which uses the scatterometry method, measures cross-sectional shape information about a test pattern, an electron microscope obtains an electron beam image of an arbitrary pattern, and the cross-sectional shape information about the test pattern is applied to slope change information about a surface of the fine pattern reflected on the electron beam image, so as to measure the three-dimensional shape of the fine pattern.
Further, in accordance with the present invention, an optical measurement system, such as scatterometry method, measures cross-sectional shape information about a test pattern, an electron microscope also obtains an electron beam image of a test pattern, a relational equation is derived from the cross-sectional shape information and the electron beam image, and the relational equation is applied to an electron beam image of a fine pattern, so as to measure the three-dimensional shape of the fine pattern. Further; in accordance with the present invention, cross sectional shape information about a test pattern is obtained by an optical measurement system, such as a system which uses the scatterometry method, and the obtained information is used as a constraint for calculating a three dimensional shape of a fine pattern through the following methods (1) and (2).
(1) With a plurality of the images that are obtained when a fine pattern tilts at different angles, which images are obtained by an electron microscope having a beam tilt or stage tilt system, a three dimensional shape of the fine pattern is measured based on the principle of triangulation.
(2) With a plurality of reflected electron beam images that are obtained by a plurality of reflected electron detectors, a three dimensional shape of a fine pattern is measured on the principle of photometric stereo processing.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.
The present invention will be explained below with reference to the appended drawings.
As shown in
Actually, as shown in
The equation 5.1 of
In the present embodiment, on the principle of stereoscopic processing, a three dimensional shape of a sample is obtained from a plurality of images of the sample whose tilt angle changes using an electron microscope having a beam tilt or stage tilt system.
The bright band widths E1 and E2 of the images are measured to determine a tilt angle θ of the side surface. The tilt angle θ is inserted in an equation 7.2 to determine the height H0. The widths E1 and E2 change depending on the measurement points of an actual sample. Thus, it is necessary to determine which point on
In this embodiment, on the principle of photometric stereo processing, as shown in
In an equation 9.1, K needs to be experimentally determined by measuring signal strengths A and B of a sample having a known slope angle θ. In this embodiment, a test pattern is measured by both scatterometry and a SEM, θ is determined from a result of measurement by scatterometry, and the signal strengths A and B are inserted in the equation 9.1 to determine K. Once K is determined, the cross-sectional shape can be determined from the signal strengths of reflected electron beam images of an arbitrary pattern. In the second embodiment, it was necessary to search for the corresponding points. In this embodiment, reflected electrons are simultaneously obtained by the two, right and left, reflected electron beam detectors, so that two images of the same point are obtained. As a result, it is not necessary to search the corresponding points.
The actual cross-sectional shape of the sample is not a trapezoid as shown in
[Usage in Semiconductor Processing]
With such a system, the scatterometry device 110 and the SEM 111 measure three dimensional shapes of resist patterns formed on a wafer through the resist exposure/development processing 120 so as to monitor the resist exposure/development processing 120.
The scatterometry device 110 and the SEM 111 measure three dimensional shapes of semiconductor devices and circuit patterns that are formed on a wafer through the etching processing 130 in order to monitor the etching processing 130.
The three dimensional shape measurement data of the resist patterns and that of the element and circuit patterns are transmitted via the communication line 150 to the QC data collection/analysis system 142, where the relationship between both data is analyzed. In accordance with the analysis result and work record data stored in the work record management system 141, resist exposure/development processing and etching processing recipes stored in the recipe server 140 can be controlled.
[Method for Displaying Results]
A diagram showing the cross-sectional shape of the pattern and shape data of each portion of the cross-section are displayed as a result of the three dimensional measurement. When the pattern is formed of a plurality of layers, cross-sectional shape data of each layer may be displayed.
Like the display in
A diagram showing the cross-sectional shape of the pattern and shape data of each portion of the cross-section are displayed as a result of the three dimensional measurement. Cross-sectional shape data of each layer also may be displayed. This is because, when the pattern is formed of a plurality of layers, the detection signal changes depending on the secondary electron emission efficiency of each layer, so that each layer can be recognized to determine the cross-sectional shape data of each layer.
As described above, according to the present invention, the three dimensional shape of a fine pattern formed on a semiconductor device, such as a semiconductor memory and an integrated circuit, can be measured more precisely without deconstructing the semiconductor device.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
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|International Classification||H01L21/66, H01L23/544, G06K9/00, H01J37/22, G01B15/00, G01N21/956, G06T7/00|
|Cooperative Classification||H01L22/34, G06T2207/30148, G01N21/956, G06T7/0004, H01L2924/0002|
|European Classification||H01L22/34, G06T7/00B1|
|Oct 7, 2003||AS||Assignment|
Owner name: HITACHI HIGH-TECHNOLOGIES CORPORATION, JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SHISHIDO, CHIE;NAKAGAKI, RYO;TANAKA, MAKI;AND OTHERS;REEL/FRAME:014596/0935;SIGNING DATES FROM 20030902 TO 20030919
|Jun 27, 2012||FPAY||Fee payment|
Year of fee payment: 4